[DOC] Fixed Developer Setup Link in install.rst

[RaunakJalan]

Summary

Changed the link for developer setup in install.rst to make it working. Previously showing Error 404.
Now the link is working and redirecting to appropriate page.

List of changes proposed in this PR (pull-request)

• Change link of developer setup to <../devel/testing_nipype.rst> instead of <../devel/testing_nipype.html>

Acknowledgment

• (Mandatory) I acknowledge that this contribution will be available under the Apache 2 license.

[codecov]

Codecov Report

Merging #3330 (dc57459) into master (89d828c) will increase coverage by 0.04%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #3330 +/- ## ========================================== + Coverage 65.05% 65.09% +0.04%  ========================================== Files 302 302 Lines 40027 40027 Branches 5292 5292 ========================================== + Hits 26038 26055 +17  + Misses 12916 12904 -12  + Partials 1073 1068 -5 

Flag	Coverage Δ
unittests	65.01% <ø> (+0.04%)	⬆️

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Impacted Files	Coverage Δ
nipype/pipeline/plugins/base.py	59.72% <0.00%> (+1.64%)	⬆️
nipype/pipeline/plugins/legacymultiproc.py	71.07% <0.00%> (+5.39%)	⬆️

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[effigies]

Great, thanks! Would you like to add yourself to the .zenodo.json file?

[RaunakJalan]

Yeah sure @effigies. I would like to add myself to it. Looking to make more contributions in future.

[effigies]

Sounds great! Just add your information after this entry: https://github.com/RaunakJalan/nipype/blob/doc_issue/.zenodo.json#L796-L800